1. Field of the Invention
The present invention relates to a system for speech enhancement in a room comprising a microphone for capturing audio signals from a speaker's voice, an audio signal processing unit for processing the captured audio signals and a loudspeaker arrangement located in the room for generating amplified sound according to the processed audio signals.
By using such a system, the speaker's voice can be amplified in order to increase speech intelligibility for persons present in the room, such as the listeners in an audience or pupils/students in a classroom. However, increased amplification does not necessarily result in increased speech intelligibility.
2. Description of Related Art
U.S. Pat. No. 7,333,618 B2 relates to a speech enhancement system comprising, in addition to the speaker's microphone, a second microphone placed in the audience for capturing both the sound generated by the loudspeakers and ambient noise, a variable amplifier and an ambient noise compensation circuit. The output signal of the variable amplifier is compared to the ambient noise level derived from the signals captures by the second microphone, and the gain applied to the signals from the speaker's microphone is adjusted according to the level of the ambient noise.
European Patent Application EP 1 691 574 A2 relates to an FM (frequency modulation) transmission system for a hearing aid, wherein the gain applied to the audio signals captured by the microphone of the FM transmission unit is adjusted in the FM receiver according to the ambient noise level and the voice activity as detected by analyzing the audio signals captured by the microphone. The gain is automatically increased when as it is detected that the speaker is speaking; the gain is also adjusted as a function of ambient noise level.